Compensating plunger for solenoid valve and method of making

ABSTRACT

A fluid control valve for an hydraulic system and having a compensating plunger movable in response to energization of a solenoid to alter the path of hydraulic fluid flow through the valve. The plunger is generally cylindrical and has a bore extending axially therethrough and containing elastomeric inserts at opposite ends thereof. Each insert has a seating surface for sealing engagement with a respectively associated valve seat. One of the inserts is movable relative to the plunger and spring biased to its seating position. The inserts are constructed and arranged so that the portion of each insert which defines the seating surface thereof is substantially free of internal stress.

United States Patent 1 Allen COMPENSATING PLUNGER FOR SOLENOID VALVE ANDMETHOD OF MAKING [75] Inventor: Walter E. Allen, Prospect, Conn.

[73] Assignee: Peter Paul Electronics, New Britain,

Conn.

[22] Filed: June 10, 1971 [21] Appl. No.: 151,811

[52] U.S.Cl ..251/l4l,137/625.5

[ 51 May 15, 1973 2,414,577 1/1947 Adair et al ..1 37/434 2,469,1095/1949 Goecke 3,185,177 5/1965 Brandenberg et a1. ..l37/625.27 3,215,90211/1965 Foley et a1. 251/141 X 3,351,093 11/1967 Frantz ...137/625.273,608,585 9/1971 Huntington ..251/141 X Primary ExaminerSamuel Scott Attorney- McCormick, Paulding & Huber [57] ABSTRACT A fluid control valvefor an hydraulic system and having a compensating plunger movable inresponse to energization of a solenoid to alter the path of hydraulicfluid flow through the valve. The plunger is generally cylindrical andhas a bore extending axially therethrough and containing elastomericinserts at opposite ends thereof. Each insert has a seating surface forsealing engagement with a respectively associated valve seat. One of theinserts is movable relative to the plunger and spring biased to itsseating position. The inserts are constructed and arranged so that theportion of each insert which defines the seating surface thereof issubstantially free of internal stress.

12 Claims, 9 Drawing Figures PATENTEDHAY] SL975 3,047

SHEET 1 OF 2 FIG. 1

2 i 58 v 12 55 4O 54 Q IO INVENTOR l WALTER E. ALLEN ATTORNEYSPATEMEBMY] 51675 33,047

SHEET 2 [1F 2 BACKGROUND OF THE INVENTION This invention relates ingeneral to solenoid actuated fluid control valves and deals moreparticularly with an improved compensating plunger for an hydraulic con-.trol valve and a method for making same.

I Compensating plungers have been provided for bydraulic valves of theaforedescribed type and such plungers usually include at least onemovable insert assembly comprising a tubular shell supported for slidingmovement in the plunger and containing an elastomeric insert for sealingengagement with an associated valve seat. A plunger of theaforedescribed type may also include a fixed insert which is retained ina stationary position in the plunger. In an hydraulic system substantialforces are often developed which may tend to draw or suck a movableinsert out of its shell or to dislodge an associated stationary insert.For this reason, it is essential that insert assemblies for suchinstallations have a high degree of insert retention capability. Here:tofore, such insert assemblies have been provided with precisionmachined shells made from stainless steel or like material, andelastomeric inserts molded therein or otherwise forcibly assembledtherewith. Forcible assembly of the elastomeric insert with an insertshell or plunger may, and often does, damage or otherwise deform theinsert material thereby impairing its sealing capability. Wherecompression of the insert materials is relied upon for retention of theinsert within the shell or plunger, internal stresses produced in theinsert material tend to further impair the seating capability of theinsert. For the aforesaid reasons, insert assemblies of the molded typeare preferred, however, such insert assemblies are considerably morecostly to produce and lack the insert retention characteristics of theforcibly assembled type. Accordingly, it is the general aim of thepresent invention to provide a compensating plunger for economicalproduction and having improved sealing and insert retentioncharacteristics, and

to provide an improved method for making same.

SUMMARY OF THE INVENTION ing an associated valve seat.

BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a vertical sectional viewthrough a solenoid actuated fluid control valve having a compensatingplunger made in accordance with the present invention.

FIG. 2 is a somewhat enlarged vertical sectional view through theplunger of FIG. 1 taken along the line 2-2 of FIG. 1.

FIG. 3 is an exploded view of the plunger of FIG. 2 rotated 180 from itsposition in FIG. 2.

FIG. 4 is a somewhat further enlarged view illustrat ing a method formaking a plunger insert assembly, the tools used in making the assemblybeing shown somewhat schematically and partially in section.

FIG. 5 is a vertical sectional view through another compensating plungermade in accordance with the present invention.

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5.

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 5.

FIG. 8 is a somewhat enlarged fragmentary vertical sectional view of aportion of the plunger of FIG. 5.

FIG. 9 is a somewhat enlarged fragmentary vertical sectional view ofanother portion of the plunger of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to thedrawing and referring particularly to FIG.'1, a compensating plungerconstructed in accordance with the present invention and indicatedgenerally at 10 comprises part of a solenoid actuated fluid controlvalve indicated generally at 12. The valve 12 is particularly adaptedfor use in an hydraulic system and has a body 14 defining a chamber 16containing the plunger 10. More specifically, the body 14 includes ahollow generally cylindrical base 18, an annular con necting nut 20threadably received in the upper end of the base 18 and a generallycylindrical tubular sleeve 22 which is carried by the nut 18 and extendsaxially upwardly therefrom. The sleeve 22 is made from nonmagneticmaterial and has a generally cylindrical bore 24, the upper end of whichis closed by a plug 26 welded or otherwise suitably secured thereto. Apair of diametrically opposed internally threaded horizontal fluid flowports 28 and 30 in the base 18 are adapted to receive pipe connectionsor other fluid conduit fittings for connecting the valve 12 to anassociated hydraulic system. The port 28 communicates with the chamber16 through fluid passageways 32 and 34. An upwardly facing annular valveseat 36 coaxially aligned with the bore 24 surrounds the upper end ofthe passageway 34. The other port 30 is connected to the chamber 16 by afluid passageway 38. Still another fluid passageway 40 extendsdownwardly through the plug 26 and has a downwardly facing annular valveseat 42 at its lower end coaxially aligned with the bore 24.

The plunger 10, hereinafter more fully described, has a generallycylindrical body 44 guided for axial sliding movement in the chamber 16by the bore 24 which partially defines the latter chamber. The plungercontains a movable insert assembly 46, a compensating spring 48, and afixed insert or plug which retains the movable insert and the spring inassembly with the plunger. The spring 48 acts between the plug 50 andthe movable insert 46 to bias the latter insert upwardly or toward thevalve seat 42.

The plunger 10 is biased toward seating engagement with the valve seat36 by a spring 52 which acts between the nut 20 and an annular flange atthe lower end of the plunger body. An annular magnet coil 54 surroundsthe sleeve 22. Preferably, and as shown, a housing 55 surrounds themagnet coil 54 and is retained in assembly with the body 14 by aconnecting nut 56 which threadably engages the plug 26. The nut 56 hasan internally threaded port 58 for receiving a pipe connection or otherfluid conduit fitting for connecting the passageway 40 to an hydraulicsystem.

When the magnet coil 54 is in a de-energized state, the plunger 10 isbiased to the position shown in FIG.

1 so that the plug 50 is in sealing engagement with the valve seat 36.The ports 30 and 58 are connected by the passageways 38 and 40 andchamber 16 so that fluid may flow therebetween. When the magnet coil 54is energized, the plunger is drawn upwardly in the bore 24 and intoseating engagement with the valve seat 42 thereby sealing the passageway40 and the port 58 against fluid flow thereto. When the plunger 10 is inthe latter position, the ports 28 and 30 are connected by thepassageways 32, 34 and 38 and the chamber 16 so that fluid may flowtherebetween. The valve 12 and its operation have been generallydescribed. However, for a more detailed description of a valve of thistype, reference may be had to U.S. Pat. No. 3,307,129 to Mangiafico,issued February 28, 1967, and titled Solenoid Operator for a Valve orthe Like.

Considering now the plunger 10 in further detail and referringparticularly to FIGS. 2 and 3, the plunger body 44 is made from magneticmaterial and has an annular flange 62 which surrounds one end thereof toprovide a bearing surface for the spring 52. A plurality of axiallyextending radially outwardly opening grooves 64, 64 are formed in theplunger body to permit fluid .to flow upwardly in the chamber 16 betweenthe plunger 10 and the sleeve 22. A generally cylindrical vbore 66extends coaxially through the body 44 and openings 68, 68 formed in thebody wall communicate with the bore 66 to provide for equilization offluid pressure within the bore 66 and the chamber 16. The bore 66 has areduced diameter portion 70 at one end thereof. An inwardly facingannular shoulder 72 provides transition between the main portion of thebore 66 and the reduced portion 70. At the other end of the bore 66there is an annular recess 74 defined by an enlarged bore potion 76 andan outwardly facing annular shoulder 78. Another annular recess 80 isformed in the body wall spaced inwardly from the recess 74. The recess80 is partially defined by an enlarged bore portion 82 and an inwardlyfacing annular shoulder 84. The plunger bore 66 also includes a conicaltransition por tion 86 diverging inwardly from the annular shoulder 78toward the recess 80.

The insert assembly 46 generally comprises a thinwalled tubular shell 88containing an elastomeric insert 90. The shell 88 is made from flatmetal, such as stainless steel, cut and drawn on an eyelet press or likemachine and is adapted to be slidably received in the upper end of theplunger bore, as the plunger appears oriented in FIG. 2. It has anenlarged cylindrical portion 92, the outside diameter of which issubstantially equal to the inside diameter of the main bore portion 66.It also has a reduced cylindrical portion 94 which has an outsidediameter substantially equal to the diameter of the bore portion 70. Atransitional portion 96 connects the cylindrical portions 92 and 94 andis adapted to engage and substantially complement the.

annular shoulder 72 when the insert is assembled with the plunger. Theelastomeric insert 90 is received in and substantially complements anassociated portion of the shell 88. It includes a cylindrical portion 98and a somewhat larger cylindrical portion 100. The cylindrical portion98 has a seating surface 95 and an outside diameter substantially equalto the inside diameter of the shell portion 94 in which it is received.Consequentially, no substantial compressive stress is exerted upon theinsert portion 98 by the associated shell portion 94 so that nosubstantial internal stresses are produced in the elastomeric insertmaterial in the vicinity of the seating surface to impair the sealingcharacteristics of the insert. The outside diameter of the cylindricalportion 100 is substantially greater than the inside diameter of theshell portion 92 which receives it. Thus, the cylindrical portion 100 issubjected to substantial compressive stress by the associated shellportion 92 which gives the insert assembly 46 great insert retentioncapability.

The insert assembly 46 is completed by forcibly inserting the insert 90into the shell 88. Preferably, the insert portion 100 is compressed toreduce its diameter to at least equal the inside diameter of thecylindrical portion 92. The insert 90 is then inserted into the shell 88while the insert portion 100 is maintained in compression.

A preferred method for assembling the insert in the shell is illustratedin FIG. 4. In accordance with this preferred method the shell issupported in a fixture 102, substantially as shown. A jig 104 having agenerally conical opening 106 extending therethrough is then positionedadjacent the end of the enlarged portion 92. The opening 106 has a majordiameter at least equal to and preferably somewhat greater than thediameter of the insert portion 100 before assembly. The minor diameterof the conical opening is at least as small as the inside diameter ofthe enlarged portion 92. Assembly is effected by applying a tool such asindicated at 107 to force the insert 90 downwardly through the opening106 and into the shell 88, substantially as illustrated.

The plug 50, best shown in FIG. 3, is adapted for interlockingengagement with the body 44, provides a seating surface for the valveseat 36 and retains the insert assembly 46 and the spring 48 in assemblywith the plunger as previously noted. It is preferably molded fromelastomeric material for snap-fit engagement with the plunger body andhas a radially outwardly projecting annular flange 108 adapted to bereceived in the annular recess 80 and partially defined by an axiallyoutwardly facing annular shoulder 110 for engaging the inwardly facingshoulder 84. The inner end of the plug 50 has a truncated conicalconfiguration for cooperating with the conical surface 86 to guide theplug into assembly with the plunger body 44. At its outer end, the plug50 has another annular flange 112 adapted to be received in the recess74 and partially defined by an axially inwardly facing annular abutmentsurface 114 for engaging the bearing surface 78 and a generally radiallydisposed outwardly facing seating surface 116. The outside diameter ofthe flange 112 is substantially equal to the inside diameter of therecess 74 so that substantially no internal stresses are developed inthe flange portion of the plug to impair the sealing characteristics ofthe seating surface 116. In assembly, the plug surfaces 1 l0 and l 14,respectively, cooperate with the plunger body surfaces 84 and 78 toretain the plug and plunger in assembled relationship.

The plunger 10 is preferably assembled as illustrated in FIG. 3. Theplunger body 44 is inverted so that the reduced bore portion 70 ispositioned at the lower end thereof. The insert assembly 46 and thespring 48 may then be dropped into the bore 66. The conical bore portion72 serves to guide the insert assembly 46 into a properly seatedposition. Thereafter, the plug 50 is forcibly inserted in the body 44 tocomplete the plunger assembly. If desired, an appropriate jig andfixsured.

ture, such as illustrated in FIG. 4, may be provided to aid in assemblyof the plug in the plunger body.

In a compensating plunger for an hydraulic valve or the like wherein arelatively high compensating spring force is employed, it is preferablethat means be provided to prevent the compensating spring from hearingdirectly upon the elastomeric insert material. This arrangement preventsthe compensating spring from deforming the insert material or causinginternal stresses therein which may impair the sealing characteristicsof the material. A compensating plunger of the latter type, made inaccordance with the present invention, is illustrated in FIGS. 5-9 andindicated generally at a. The plunger 10a is similar in many respects tothe plunger 10 and parts thereof which are substantially identical to ofwhich is chamfered as indicated at 126 and best transitional portionbetween said main portion and said one end portion, an insert assemblyslidably received in said bore and including a relatively thin-walledtubular shell and an elastomeric insert received in said shell, saidshell having a generally cylindrical enlarged portion received in saidmain bore portion, a generally cylindrical reduced potion received inand having a diameter substantially equal to the diameter of said oneend portion and an intermediate portion between said enlarged andreduced portions for engaging said transitional portion, said inserthaving a generally cylindrical first portion received in said reducedportion and defining a radially disposed seating surface exposed at saidone end of said plunger when said intermediate portion is in engagementwith said transitional portion, said first portion having a diameterbefore assembly with said shell substantially equal tothe insidediameter of said reduced portion so that no substantial compressivestress is exerted upon said first portion by said reduced portion in thevicinity of said seating surface, said insert including a secondgenerally cylindrical portion having a diameter before assembly greaterthan the inside diameter of said enlarged portion, said insert beingretained in assembly with said shell by radially inwardly I directedcompressive force exerted upon said second portion by said enlargedportion, a spring received in said bore for biasing said insert assemblytoward said shown in FIG. 8. An elastomeric insert a received within theshell 122 is assembled therewith in the manner previously described sothat no substantial internal stresses are developed by the insert in thevicinity of its seating surface a. The compensating spring is preventedfrom bearing directly against the insert 90a by a bearing washer or disc128 received within the enlarged portion 124 and bearing upon thechamfered edge 126. The spring 120 engages the bearing washer 128 whichtransmits biasing force to the shell 122 and isolates the insert 90afrom direct contact with the spring 120.

In a like manner, the plug 50a is isolated from the spring 120 by aresilient retaining washer 130 received within the bore 66a between thespring 120 and the plug 50a. The washer 130 is preferably made frommaterial harder than the material of the body 44a and includes aplurality of generally radially outwardly extending legs 132, 132. Eachleg 132 is bent out of the plane of the washer 130 and in the directionof the plug 50a as by forcible insertion of the washer into the bore 66athrough the plug end thereof. Each leg 132 has a sharp edge 134 thereonfor incising the wall of the bore 66a so that the washer 130 grippinglyengages the latter wall. It will be apparent that the biasing forceexerted by the spring 120 causes the washer 130 to bite into the wall ofthe bore 66a, thereby preventing the spring 120 from exerting biasingforce upon the plug 50a. In this manner, effective sealing engagementbetween the plug seating surface 116a and an associated valve seat isas- I claim:

1. A compensating plunger for a solenoid valve, said plunger having anaxially elongated generally cylindrical body including a bore extendingcoaxially therethrough, said bore including a generally cylindrical mainportion and one end portion having a diameter substantially smaller thanthe diameter of said main portion, said bore including an inwardlyfacing annular one end portion, and means for retaining said spring insaid bore.

2. A compensating plunger as set forth in claim 1 wherein saidtransitional portion comprises a generally conical portion divergingfrom said one end portion to said main portion.

3. A compensating plunger as set forth in claim 1 .wherein said meansfor retaining said spring comprises an elastomeric plug received insnap-fit engagement with'said body in the other end of said bore, saidplug having a generally radially disposed bearing surface exposed atsaid other end.

4. A compensating plunger as set forth in claim 1 wherein said means forretaining said spring comprises a retaining washer received in said borein gripping engagement with the wall thereof.

5. A compensating plunger as set forth in claim 4 wherein said retainingwasher is further characterized as a resilient washer having a pluralityof generally radially outwardly extending legs in gripping engagementwith the wall of said bore.

6. A compensating plunger as set forth in claim 5 wherein said washer ismade from material harder than the material of said body, said legsincising the wall of said bore in gripping engagement therewith.

7. A compensating plunger as set forth in claim 1 including a bearingmember between. said spring and said insert assembly and engaging saidshell, said spring engaging said bearing member for biasing said insertassembly toward said one end portion.

8. A compensating plunger as set forth in claim 7 wherein said secondportion has a chamfered inner edge and said bearing member is receivedwithin said second portion and engages said chamfered inner edge.

9. A compensating plunger for a solenoid valve, said plunger having anaxially elongated generally cylindrical body including a bore extendingcoaxially therethrough, said bore including a generally cylindrical mainportion and one end portion having a diameter substantially smaller thanthe diameter of said main portion, said bore including an inwardlyfacing annular transitional portion between said main portion and saidone end portion, said bore having an enlarged generally cylindricalportion opening through the other end of said plunger and partiallydefined by an axially outwardly facing annular bearing surface and aradially inwardly opening annular recess spaced axially inwardly fromsaid outwardly facing bearing surface and partially defined by anaxially inwardly facing annular shoulder, said plunger bore furtherincluding a conical portion converging from said enlarged bore portiontoward said recess, an insert assembly slidably received in said boreand including a thin-walled tubular shell and an elastomeric insert,said shell having a generally cylindrical enlarged portion received insaid main bore portion, a generally cylindrical reduced portion receivedin and having a diameter substantially equal to the diameter of said oneend portion and an intermediate portion between said enlarged andreduced portions for engaging said transitional portion, saidelastomeric insert received in said shell and defining a radiallydisposed seating surface exposed at said one end of said bore when saidintermediate portion is in engagement with said transitional portion, aspring received in said bore for biasing said insert assembly towardsaid one end, and an elastomeric plug received in the other end of saidbore, said plug having a generally cylindrical flange portion receivedin said enlarged bore portion and partially defined by a radiallyinwardly facing abutment surface engaging said bearing surface, saidflange portion having a diameter substantially equal to said enlargedbore portion and defining a radially disposed outwardly facing seatingsurface, said plug further including a radially outwardly projectingannular portion received in said annular recess and partially defined byan axially outwardly facing annular shoulder engaging said inwardlyfacing shoulder, said recess and said outwardly projecting portion ofsaid plug comprising means for retaining said plug in said bore.

10. A- compensating plunger for a solenoid valve, said plunger having anaxiallyelongated generally cylindrical body including a bore extendingcoaxially therethrough, said bore including a generally cylindrical mainportion and one end portion having a diameter substantially smaller thanthe diameter of said main portion, said bore including an inwardlyfacing annular transitional portion between said main portion and saidone end portion, said bore having an enlarged generally cylindricalportion opening through the other end of said plunger and partiallydefined by an axially outwardly facing annular bearing surface, aninsert assembly slidably received in said bore and including athinwalled tubular shell and an elastomeric insert, said shell having agenerally cylindrical enlarged portion received in said main boreportion, a generally cylindrical reduced portion received in and havinga diameter substantially equal to the diameter of said one end portionand an intermediate portion between said enlarged and reduced portionsfor engaging said transitional portion, said elastomeric insert receivedin said shell and defining a radially disposed seating surface exposedat said one end of said bore when said intermediate portion is inengagement with said transitional portion, a retaining washer receivedin said bore in gripping engagement with the wall of said bore, a springreceived in said bore between said washer and said insert assembly forbiasing said insert assembly toward said one end, said spring having oneend thereof bearing against said insert assembly and the other endthereof bearing against said washer, an elastomeric plug received in theother end of said bore, said plug having a generally cylindrical flangeportion received in said enlarged bore portion and partially defined bya radially inwardly facing abutment surface engaging said bearingsurface, said flange portion having a diameter substantially equal tosaid enlarged bore portion and defining a radially disposed outwardlyfacing seating surface, and means for retaining said plug in said bore.

11. A compensating plunger as set forth in claim 10 wherein saidretaining washer is further characterized as a resilient washer having aplurality of generally radially outwardly extending legs engaging thewall of said bore.

12. A compensating plunger as set forth in claim 11 wherein saidresilient washer is made from material harder than the material of saidbody, said legs incising the wall of said bore in gripping engagementtherewith.

1. A compensating plunger for a solenoid valve, said plunger having anaxially elongated generally cylindrical body including a bore extendingcoaxially therethrough, said bore including a generally cylindrical mainportion and one end portion having a diameter substantially smaller thanthe diameter of said main portion, said bore including an inwardlyfacing annular transitional portion between said main portion and saidone end portion, an insert assembly slidably received in said bore andincluding a relatively thin-walled tubular shell and an elastomericinsert received in said shell, said shell having a generally cylindricalenlarged portion received in said main bore portion, a generallycylindrical reduced potion received in and having a diametersubstantially equal to the diameter of said one end portion and anintermediate portion between said enlarged and reduced portions forengaging said transitional portion, said insert having a generallycylindrical first portion received in said reduced portion and defininga radially disposed seating surface exposed at said one end of saidplunger when said intermediate portion is in engagement with saidtransitional portion, said first portion having a diameter beforeassembly with said shell substantially equal to the inside diameter ofsaid reduced portion so that no substantial compressive stress isexerted upon said first portion by said reduced portion in the vicinityof said seating surface, said insert including a second generallycylindrical portion having a diameter before assembly greater than theinside diameter of said enlarged portion, said insert being retained inassembly with said shEll by radially inwardly directed compressive forceexerted upon said second portion by said enlarged portion, a springreceived in said bore for biasing said insert assembly toward said oneend portion, and means for retaining said spring in said bore.
 2. Acompensating plunger as set forth in claim 1 wherein said transitionalportion comprises a generally conical portion diverging from said oneend portion to said main portion.
 3. A compensating plunger as set forthin claim 1 wherein said means for retaining said spring comprises anelastomeric plug received in snap-fit engagement with said body in theother end of said bore, said plug having a generally radially disposedbearing surface exposed at said other end.
 4. A compensating plunger asset forth in claim 1 wherein said means for retaining said springcomprises a retaining washer received in said bore in grippingengagement with the wall thereof.
 5. A compensating plunger as set forthin claim 4 wherein said retaining washer is further characterized as aresilient washer having a plurality of generally radially outwardlyextending legs in gripping engagement with the wall of said bore.
 6. Acompensating plunger as set forth in claim 5 wherein said washer is madefrom material harder than the material of said body, said legs incisingthe wall of said bore in gripping engagement therewith.
 7. Acompensating plunger as set forth in claim 1 including a bearing memberbetween said spring and said insert assembly and engaging said shell,said spring engaging said bearing member for biasing said insertassembly toward said one end portion.
 8. A compensating plunger as setforth in claim 7 wherein said second portion has a chamfered inner edgeand said bearing member is received within said second portion andengages said chamfered inner edge.
 9. A compensating plunger for asolenoid valve, said plunger having an axially elongated generallycylindrical body including a bore extending coaxially therethrough, saidbore including a generally cylindrical main portion and one end portionhaving a diameter substantially smaller than the diameter of said mainportion, said bore including an inwardly facing annular transitionalportion between said main portion and said one end portion, said borehaving an enlarged generally cylindrical portion opening through theother end of said plunger and partially defined by an axially outwardlyfacing annular bearing surface and a radially inwardly opening annularrecess spaced axially inwardly from said outwardly facing bearingsurface and partially defined by an axially inwardly facing annularshoulder, said plunger bore further including a conical portionconverging from said enlarged bore portion toward said recess, an insertassembly slidably received in said bore and including a thin-walledtubular shell and an elastomeric insert, said shell having a generallycylindrical enlarged portion received in said main bore portion, agenerally cylindrical reduced portion received in and having a diametersubstantially equal to the diameter of said one end portion and anintermediate portion between said enlarged and reduced portions forengaging said transitional portion, said elastomeric insert received insaid shell and defining a radially disposed seating surface exposed atsaid one end of said bore when said intermediate portion is inengagement with said transitional portion, a spring received in saidbore for biasing said insert assembly toward said one end, and anelastomeric plug received in the other end of said bore, said plughaving a generally cylindrical flange portion received in said enlargedbore portion and partially defined by a radially inwardly facingabutment surface engaging said bearing surface, said flange portionhaving a diameter substantially equal to said enlarged bore portion anddefining a radially disposed outwardly facing seating surface, said plugfurther including a radially outwardly projecting annular portionreceived in said annular Recess and partially defined by an axiallyoutwardly facing annular shoulder engaging said inwardly facingshoulder, said recess and said outwardly projecting portion of said plugcomprising means for retaining said plug in said bore.
 10. Acompensating plunger for a solenoid valve, said plunger having anaxially elongated generally cylindrical body including a bore extendingcoaxially therethrough, said bore including a generally cylindrical mainportion and one end portion having a diameter substantially smaller thanthe diameter of said main portion, said bore including an inwardlyfacing annular transitional portion between said main portion and saidone end portion, said bore having an enlarged generally cylindricalportion opening through the other end of said plunger and partiallydefined by an axially outwardly facing annular bearing surface, aninsert assembly slidably received in said bore and including athin-walled tubular shell and an elastomeric insert, said shell having agenerally cylindrical enlarged portion received in said main boreportion, a generally cylindrical reduced portion received in and havinga diameter substantially equal to the diameter of said one end portionand an intermediate portion between said enlarged and reduced portionsfor engaging said transitional portion, said elastomeric insert receivedin said shell and defining a radially disposed seating surface exposedat said one end of said bore when said intermediate portion is inengagement with said transitional portion, a retaining washer receivedin said bore in gripping engagement with the wall of said bore, a springreceived in said bore between said washer and said insert assembly forbiasing said insert assembly toward said one end, said spring having oneend thereof bearing against said insert assembly and the other endthereof bearing against said washer, an elastomeric plug received in theother end of said bore, said plug having a generally cylindrical flangeportion received in said enlarged bore portion and partially defined bya radially inwardly facing abutment surface engaging said bearingsurface, said flange portion having a diameter substantially equal tosaid enlarged bore portion and defining a radially disposed outwardlyfacing seating surface, and means for retaining said plug in said bore.11. A compensating plunger as set forth in claim 10 wherein saidretaining washer is further characterized as a resilient washer having aplurality of generally radially outwardly extending legs engaging thewall of said bore.
 12. A compensating plunger as set forth in claim 11wherein said resilient washer is made from material harder than thematerial of said body, said legs incising the wall of said bore ingripping engagement therewith.